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NEWS NOTES — NEWS Geoarchaeology
More than any battering ram, catapult or sword, Alexander the Great may owe his success in seizing the island of Tyre to waves and sand. In 332 B.C., after an unsuccessful seven-month blockade of the impenetrable island, Alexander reached Tyre by constructing a 1,000-meter causeway from what is modern-day Lebanon to the island. New research shows a shallow sandbar may have made this engineering feat and the infamous fall of Tyre possible. Today, Tyre is no longer an island; it is fully connected to Lebanon by a sand isthmus, or tombolo, which formed as sediments piled up due to the action of waves passing around the island. Based on aerial photographs and ancient documents, previous research suggested a sandbar might have existed at the time of Alexander the Great, say Nick Marriner and Christophe Morhange, geoarchaeologists at the Centre National de la Recherche Scientifique in Aix-en-Provence, France, who led the new study. But until now no geological evidence supported this idea. Using sediment cores and computer models, Marriner and his colleagues reconstructed the areas geological history over the past 8,000 years. A sandbar was indeed present at the time of Alexanders military operations, they report in the May 29 Proceedings of the National Academy of Sciences, making the water only 1 to 2 meters deep. Prior to our research, Marriner says, there were no real estimates for water depth. Alexander might have noticed the sandbar, suggests Jean-Daniel Stanley, a geoarchaeologist at the Smithsonian National Museum of Natural History in Washington, D.C., who was not involved in the study, by spotting wave breaks at the water surface above the underlying shallower area of the water. Marriner and the team also found that people played a role in the sandbars formation. Coastal erosion caused by farming and deforestation helped increase the rate of sedimentation between the island and the mainland. This rate of accumulation would have also increased after the construction of Alexanders bridge, which, Stanley says, would have served as a nucleus to trap more and more sediments. In addition to solving a historical question, this study demonstrates how you can use nature to your advantage, says Stanley, who says we often have negative views on what geological processes, such as erosion, do to coastal areas. But in this case, they were helpful at least if you were Alexander the Great.
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